This contract will develop a miniaturized fiber-optic probe for coherent Raman scattering (CRS) spectroscopy that fits inside a standard biopsy needle and allows real-time guidance toward tissue with a high density of malignant cells, which would be biopsied for molecular analysis while sparing uninvolved tissue. CRS is a non-destructive and highly sensitive laser spectroscopy technique for in vivo molecular profiling. Accuracy, safety and in vivo biopsy guidance will be demonstrated in a brain cancer (glioma) rat model and can be extended to other cancers in the future. It is anticipated that this approach can reduce the number of repeat biopsies required to obtain samples for diagnosis with emerging molecular profiling techniques and thus reduce cost and risk to patients.